Frequently Used Terms

NASA’s Crewed Space Programmes

Project Mercury | 1961-1963 | Project Mercury was NASA’s first foray into crewed spaceflight, with six flights being made in total. It had to prove that humans could survive and work in space.

Project Gemini | 1965-1966 | NASA’s forgotten child, Gemini was nonetheless vital to the success of the lunar landings. Ten flights were made, with the goals of proving several key elements of spaceflight that would make a mission to the Moon possible: spacewalks (or EVAs), long duration spaceflight, rendezvous, and docking.

Project Apollo | 1967-1972 | The most well-known of any of NASA’s endeavours, there were eleven Apollo missions in total. Six of them landed on the Moon.

Skylab | 1973-1974 | Skylab was the first American space station and was home to three crews of three astronauts over the course of 24 weeks.

Shuttle Program| 1981-2011 | Designed to be reusable, five Shuttles were built in total (named Columbia, Challenger, Discovery, Atlantis and Endeavour). Two – Challenger and Columbia – were lost in accidents in 1986 and 2003 respectively.


Command Module (CM) | The cone-shaped command module is best described as a taxi of sorts and was the only part of the entire Apollo spacecraft that returned to Earth. It didn’t land on the Moon, but stayed in orbit around it and was responsible for ferrying the crews to the Moon and back. It also housed the heat shield needed to make a safe re-entry through the atmosphere and parachutes for a landing at sea.

Apollo 11’s command module, named Columbia, floats in the Pacific after splashdown | Credit: NASA

Service Module | The cylindrical service module was responsible for providing propulsion, electrical power, oxygen and water to the command module. Unlike the command module and lunar module, astronauts couldn’t actually go into the service module. It was an explosion in this part of the spacecraft that caused Apollo 13’s extensive and life-threatening problems in 1970. Each Apollo mission’s service module was jettisoned just before re-entry and burned up in the atmosphere.

Apollo 14’s Command Module, named Kitty Hawk, joined to its Service Module | Credit: NASA

Lunar Module | The lunar module (or LM, pronounced as ‘lem’), as the name would suggest, was the part of the Apollo spacecraft that actually landed on the Moon. It was made up of two further parts: the descent stage and the ascent stage. The descent stage housed the landing gear and the rocket the astronauts used to control their landing, and was left on the Moon at the end of the mission, acting as a launchpad for the ascent stage. The ascent stage housed the cabin used by the astronauts to sleep in and another rocket engine used to get them off the surface and back into lunar orbit. Once re-docked with the command module, the ascent stage was jettisoned.

Apollo 12’s Alan Bean works in front of their lunar module, named Intrepid | Credit: NASA


Astronaut Positions (Project Apollo)

Commander (CDR)| The commander was responsible for the success of the mission and the safety of both crew and spacecraft. They were the ones who piloted the lunar module down to the surface of the Moon and made the first steps of each mission. Example: Neil Armstrong, Apollo 11

Command Module Pilot (CMP) | The command module pilot, as the name would suggest, was responsible for the systems of the command module and for performing the majority of navigational tasks. They were also in charge of the re-docking between the command and lunar modules after the CDR and LMP lifted off from the Moon. They remained in orbit around the Moon on their own, conducting various experiments. Many would argue that NASA viewed the role of command module pilot as more important than that of the lunar module pilot, despite them not walking on the Moon. Example: Mike Collins, Apollo 11

Lunar Module Pilot (LMP) | The title of ‘lunar module pilot’ is something of a misnomer because, as mentioned, it was actually the commander who piloted the lunar module down to the surface of the Moon. The LMP was instead in charge of monitoring the LM’s systems and essentially served as the flight engineer during the descent to the Moon. Example: Buzz Aldrin, Apollo 11


CapCom | CapCom is short for ‘capsule communicator’. The term was created during Project Mercury when the spacecrafts were still referred to as ‘capsules’. The CapCom is always an astronaut and is the only person in Mission Control able to talk directly to the crew of a mission, the idea being that they would be able to correctly interpret any ‘astronaut jargon’ used over the radio. They also would be in the best position to anticipate the needs of the crew and act as a ‘middle man’ should any problems arise.

EVA | EVA stands for ‘extravehicular activity’ and is another word for ‘spacewalk’.

Flight Directors and Flight Controllers| Flight directors are in charge of Mission Control during a spaceflight and have responsibility for the overall success of a mission, superseding even the mission’s commander. They oversee and monitor the activities of the flight controllers, each of whom specialises in a specific area (e.g. guidance and navigation, trajectory, communications).